I don't think whether the GM can handle the group size is the only variable. I played once in a game with a dozen players, and while the GM handled it fine, it still wasn't very fun for me. On the other hand some people thought it was awesome. Mostly the ones who would shout out in exhilaration when they rolled a 20. I think they liked the bigger audience.

1-2 = Requires special consideration
3-5 = Great
6-7 = The experience is being degraded
8+ = No thank you

These numbers seem to hold true regardless of system because it's more about the social dynamics: At 6+ the amount of attention that can be focused on each individual player seems to drop below a minimum threshold of engagement and the experience begins to degrade. Which would also seem to be why this delimiter is based on the number of players and not the number of characters: I've got a regular campaign in which 7 PCs are played by 5 players, for example, and it works great. But 7 PCs played by 7 players is virtually always a struggle.

The largest group I ever ran for, IIRC, was 14 players running a total of 23 characters (PCs and hirelings). That was certainly an interesting experience to have, but I don't recommend it. It prompted me to institute a table limit of 5 players for all future sessions of my open table.

If I had to pick a "golden number" for group size, it would be 5 players. At 3 players, the group virtually always sticks together which reduces the effectiveness of advanced pacing techniques and also eliminates a lot of potential situations, resulting in a flatter experience. At 4 players people will split up, but tend to stick to two teams of two. When you get 5 players, it seems like the point where groupings get more dynamic - 3 and 2, 3 and 1 and 1, 4 and 1, 2 and 2 and 1, etc. And the pairings usually aren't the same ones every time, which allows the group to explore different dynamics between the PCs.

I'd love to have about 15 players.

Not all at once, though.  3-5 is my favorite number at one time.

Over the 4 campaigns I'm currently running (2 per week), I have a total of 20 different players at this time.

Quote from: RPGPundit;922132Over the 4 campaigns I'm currently running (2 per week), I have a total of 20 different players at this time.

That's really awesome! I would love to have an available player base like that. If I have 1 or 2 players at any given time Im incredibly fortunate.

3 or 4 players and the GM is the perfect size, as far as I'm concerned. Just the right balance of variety and pace. Fewer than that and things can feel a little stagnant, more than that, and it takes forever to get anything done. That assumes it's the same 3-4 players week in, week out. Not a revolving door of a constantly changing roster.

Quote from: rgrove0172;922148That's really awesome! I would love to have an available player base like that. If I have 1 or 2 players at any given time Im incredibly fortunate.

Part of it is thanks to the very broad and interconnected community of gamers in Uruguay; and part of it is my local reputation.

Part of it is being able to cultivate gamers full time.  2 games every week!  4 different games!

On a related note, how big is your city?

Quote from: rgrove0172;922148That's really awesome! I would love to have an available player base like that. If I have 1 or 2 players at any given time Im incredibly fortunate.

Online is also good for this.

My current live group is 8 people, but online I have 2 groups, 4 and 6.  Online is a combination of older players who are busier now, local gamers, but many who come from sites like this one.

Quote from: Headless;923250Part of it is being able to cultivate gamers full time.  2 games every week!  4 different games!

On a related note, how big is your city?

About 1.5 million.